uses Classes, AdoDB, Windows, Messages, ActiveX;


const DM_Base=WM_User;
      DM_Ask=DM_Base+1;
      DM_Next=DM_Base+2;

      DM_Last=DM_Next;

type TSqlEvent=procedure(answer:integer) of object;

type
  TOpenQuery = Class(TThread)
  Public
    constructor Create(AConnectString:WideString; //as is
                       AonTerminate:TNotifyEvent; //wird ausgelöst, wenn Thread beendet oder abbricht
                       AOnSqlEvent:TSqlEvent); //wird ausgelöst, wenn neues Datenbankergebnis
    procedure Terminate; reintroduce; //Thread beenden
    function AskSQL(aSqlText:string):boolean; //neues SQL_Statement
    function NextSQL:boolean; //=SQLQuery.Next
  protected
    FQry: TADOQuery;
    FCon: TADOConnection;
    FSql: String;
    FConnectString: WideString;
    FOnSQLEvent:TSQLEvent;
    FAnswer:Integer;
    procedure Execute; override;
    procedure DoSQLCommand(var msg:TMessage); message DM_Ask;
    procedure DoSQLNext(var msg:TMessage); message DM_Next;

    procedure DoSQLEvent;
  end;

implementation

constructor TOpenQuery.Create;
begin
  inherited Create(False);
  FreeOnTerminate:=True;
  FConnectString:=aConnectString;
  onTerminate:=AonTerminate;
  FOnSQLEvent:=AOnSQLEvent;
end;

procedure TOpenQuery.Execute;
var msg:TMSG;
    VCLmsg:TMessage;
begin
  coinitialize(nil);
  FCon:=TAdoConnection.Create(nil);
  Fqry:=TAdoQuery.Create(nil);
  try
    FCon.ConnectionString:=FconnectString;
    Fqry.Connection:=FCon;
    FCon.Open;
    while not terminated and getmessage(msg,0,0,0) do
    begin
      if (msg.message>=DM_Base)and
         (msg.message<=DM_Last) then
      begin
        VCLmsg.Msg:=msg.message;
        VCLmsg.LParam:=msg.lParam;
        VCLmsg.WParam:=msg.wParam;
        VCLmsg.Result:=0;
        dispatch(VCLmsg) //Als message an die Klasse verteilen
      end else
        dispatchmessage(msg); //Windows verteilen lassen
    end;
  finally
    Fqry.Free;
    FCon.Free;
    CoUninitialize;
  end;
end;
procedure TOpenQuery.Terminate;
begin
  inherited;
  PostThreadMessage(self.ThreadID,WM_quit,0,0); //getmessage abbrechen
end;
procedure TOpenQuery.DoSQLCommand(var msg:TMessage);
var sqltext:PString;
begin
  sqlText:=PString(msg.LParam);
  Fqry.active:=false;
  Fqry.SQL.Text:=sqlText^;
  dispose(sqlText);
  Fqry.Open;
  if not Fqry.eof then
  begin
    FAnswer:=Fqry.FieldByName('zahl').AsInteger;
    synchronize(DoSQLEvent);
  end; //else Maintthread informieren
end;
procedure TOpenQuery.DoSQLNext(var msg:TMessage);
begin
  if (Fqry.Active)and (not Fqry.Eof) then
  begin
    Fqry.Next;
    FAnswer:=Fqry.FieldByName('zahl').AsInteger;
    synchronize(DoSQLEvent);
  end;// else an MainThread melden
end;

procedure TOpenQuery.DoSQLEvent;
begin
  if assigned(FonSQLEvent) then
    FOnSQLevent(FAnswer);
end;

function TOpenquery.AskSQL(ASqlText:string):boolean;
var SQLText:PString;
begin
  new(SQLText);
  SQLTExt^:=ASqlText;
  result:=PostThreadMessage(self.ThreadID,DM_Ask,0,integer(SQLText));
  if not result then
    dispose(SQLTExt);
end;
function TOpenQuery.NextSQL;
begin
  result:=PostThreadMessage(self.ThreadID,DM_Next,0,0);
end;